Artificial Disc Versus Fusion: A Prospective, Randomized Study With 2-Year Follow-up on 99 Patients

Rick C. Sasso, MD; Joseph D. Smucker, MD; Robert J. Hacker, MD; John G. Heller, MD

Disclosures

Spine. 2007;32(26):2933-2940. 

In This Article

Abstract and Introduction

Study Design. A total of 115 patients were randomized in a 1:1 ratio to a Bryan artificial disc replacement (56) or an anterior cervical fusion with allograft and a plate (59).
Objective. The purpose of this study is to examine the functional outcome and radiographic results of this prospective, randomized trial to determine the role of the Bryan artificial cervical disc replacement for patients with 1-level cervical disc disease.
Summary of Background Data. Artificial cervical disc replacement has become an option for cervical radiculopathy. Previous studies have evaluated the efficacy of this alternative without the scientific rigor of a concurrent control population. This study is a pooled data set from 3 centers involved in the U.S. FDA Investigational Device Exemption trial evaluating the Bryan artificial cervical disc.
Methods. The purpose of this study is to examine the functional outcome and radiographic results of this prospective, randomized trial to determine the role of the Bryan artificial cervical disc replacement for patients with 1-level cervical disc disease; 12-month follow-up is available for 110 patients and 24 month follow-up complete for 99 patients. There are 30 males and 26 females in the Bryan group and 32 males and 27 females in the fusion group. The average age was 43 years (Bryan) and 46 years (fusion). Disability and pain were assessed using the Neck Disability Index (NDI) and the Visual Analog Scale (VAS) of the neck and of the arm pain. SF-36 outcome measures were obtained including the physical component as well as the mental component scores. Range of motion was determined by independent radiologic assessment of flexion-extension radiographs. We report a prospective, randomized study comparing the functional outcome of cervical disc replacement to an anterior cervical fusion with results of 99 patients at 2 years. Prospective data were collected before surgery and at 6 weeks, 3, 6, 12, and 24 months after surgery.
Results. The average operative time for the control group was 1.1 hours and the Bryan Group 1.7 hours.Average blood loss was 49 mL (control) and 64 mL (Bryan). Average hospital stay was 0.6 days (control) and 0.9 days (Bryan). The mean NDI before surgery was not statistically different between groups: 47 (Bryan) and 49 (control). Twelve-month follow-up NDI is 10 (Bryan) and 18 (control) (P = 0.013). At 2-year follow-up, NDI for the Bryan group is 11 and the control group is 20 (P = 0.005). The mean arm pain VAS before surgery was 70 (Bryan) and 71 (control). At 1-year follow-up, Bryan arm pain VAS was 12 and control 23 (P = 0.031). At 2-year follow-up, the average arm pain VAS for the Bryan group was 14 and control 28 (P = 0.014). The mean neck pain VAS before surgery was 72 (Bryan) and 73 (control). One-year follow-up scores were 17 (Bryan) and 28 (control) (P = 0.05). At 2 years: 16 (Bryan) and 32 (control) (P = 0.005). SF-36 scores: Physical component- Before surgery Bryan 34 and control 32. At 24 months: Bryan 51 and control 46 (P = 0.009). More motion was retained after surgery in the disc replacement group than the plated group at the index level (P < 0.006 at 3, 6, 12, and 24 months). The disc replacement group retained an average of 7.9° of flexion-extension at 24 months. In contrast, the average range of motion in the fusion group was 0.6° at 24 months. There were 6 additional operations in this series: 4 in the control group and 2 in the investigational group. There were no intraoperative complications, no vascular or neurologic complications, no spontaneous fusions, and no device failures or explantations in the Bryan cohort.
Conclusion. The Bryan artificial disc replacement compares favorably to anterior cervical discectomy and fusion for the treatment of patients with 1-level cervical disc disease. At the 2-year follow-up, there are statistically significant differences between the groups with improvements in the NDI, the neck pain and arm pain VAS scores, and the SF-36 physical component score in the Bryan disc population.

Anterior cervical discectomy and fusion (ACDF) is a proven intervention for patients with radiculopathy and myelopathy.[1] Because of limitations specific to this procedure, investigators have developed alternatives to fusion that attempt to address kinematic and biomechanical issues.

Twenty-five percent of patients undergoing cervical fusion will have new onset of symptoms within 10 years of that fusion.[2] Other reports have helped to shed light on the recurrence of neurologic symptoms and degenerative changes adjacent to fused cervical levels.[3,4] Segments adjacent to a fusion may have an increased range of motion and increased intradiscal pressures.[5,6]

Pseudarthrosis is another complication encountered with anterior cervical fusion procedures. There is an association between the rate of pseudarthrosis and the number of levels fused. Brodke and Zdeblick reported a 97% fusion rate in single-level ACDF, which decreased to 83% with fusion at 3 levels.[7] Bohlman et al reported an 11% pseudarthrosis rate in single-level fusions that increased to 27% with multilevel fusions.[1]

Complications associated with autologous iliac crest harvest, traditionally used as a fusion graft in ACDF, are also well documented. Sandu et al reported a complication rate of 1% to 25% with such procedures.[8] Complications such as acute and chronic pain, infection, meralgia paresthetica, and pelvic fracture are known to occur at harvest donor sites.[9,10]

Total intervertebral disc replacement (TDR) is designed to preserve motion, avoid limitations of fusion, and allow patients to quickly return to routine activities. The primary goals of the procedure in the cervical spine are to restore disc height and segmental motion after removing local pathology. A secondary intention is the preservation of normal motion at adjacent cervical levels, which may be theorized to prevent later adjacent level degeneration. It avoids the morbidity of bone graft harvest.[11,12] It also avoids complications such as pseudarthrosis, issues caused by anterior cervical plating, and cervical immobilization side effects.

The first cervical disc arthroplasty clinical trial in the United States was the Bryan disc study initiated in May 2002 after a European prospective human clinical trial began in 2000.[13] The results of the European clinical trial, though neither randomized nor controlled, validated the stability, biocompatibility, and functionality predicted by preclinical testing. A prospective, randomized, controlled clinical trial was conducted to evaluate the safety and effectiveness of the Bryan cervical disc in patients with radiculopathy or myelopathy attributable to single-level cervical disc disease. The findings of this study represent a pooled data set of 3 sites from the U.S. FDA Investigational Device Exemption (IDE) study.

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